1. Field of the Invention
This invention relates to a disc apparatus for recording and/or reproducing information signals on a magnetic disc having a signal recording portion on its major surface. The present invention can be applied in particular to a magnetic disc apparatus for recording and/or reproducing information signals in a state in which the magnetic head is floated from the signal recording portion of the magnetic disc being run in rotation.
2. Description of Related Art
Up to now, a magnetic disc apparatus employing, as a recording medium, a magnetic disc, with a diameter of 3.5-inch floppy disc inch, having a signal recording portion on the major surface of a disc substrate formed of flexible synthetic resin, has been in use.
A magnetic disc 1 used in this magnetic disc apparatus has, in its center, a hub 2 comprised of a thin stainless steel plate. In the center area of the hub 2 is formed a spindle hole 3 passed through by a spindle 16 of a disc rotation unit 15 provided on the magnetic disc apparatus. At a position offset from the spindle hole 3 of the hub 2 is formed a driving pin engagement hole 4 engaged by a driving pin 17 of the disc rotation unit 15.
The magnetic disc 1 having the flexible disc substrate tends to be damaged by the slightest external force. Moreover, information signals cannot be recorded/reproduced correctly if contaminants are deposited thereon. The magnetic disc of this sort is constituted as a disc cartridge by being housed within a main cartridge body unit 7, formed on abutting and connecting an upper cartridge half and a lower cartridge half in order to prevent possible damage and deposition of contaminants. The magnetic disc 1, housed within the main cartridge body unit 7, is loaded as it is contained in the main cartridge body unit 7 on the magnetic disc apparatus, or is kept in store.
In a mid portion on the lower surface of the main cartridge body unit 7 housing the magnetic disc 1 is formed a circular center opening 9 via which a hub 2 formed at the center of the magnetic disc 1 is exposed to outside. In the upper and lower surfaces of the main cartridge body unit 7 are formed paired facing recording and/or reproducing apertures 10, 11 for extending from the vicinity of the center opening 9 to the front side so that a portion of the signal recording portion of the magnetic disc is exposed to outside across the inner and outer rims of the disc.
Although not shown, a shutter for opening or closing the recording and/or reproducing apertures is movably mounted on the main cartridge body unit 7.
On the magnetic disc apparatus on which to load the above-described disc cartridge is mounted a disc rotation unit 15 adapted for running the magnetic disc 1 housed in the disc cartridge 8 in rotation. The disc rotation unit 15 includes a spindle motor, mounted on a base, not shown, provided in the main body portion of the apparatus, and a disc table 20 mounted on the distal end of the spindle 19 of the spindle motor for rotation in unison therewith, as shown in FIG. 1. On the surface of the disc table 20, on which to set the magnetic disc 1, there is mounted a magnet 21 for sucking the hub 2 mounted on the magnetic disc 1. On the magnetic disc setting surface of the disc table 20 at a position offset from the spindle 19 is protuberantly formed the driving pin 17 engaged in the driving pin engagement hole 4 formed in the hub 2. The driving pin 17 is biased towards the outer rim of the disc table 20 by a biasing member, such as a tension spring, not shown.
When the disc cartridge 8 is loaded in position on the cartridge loading unit in the magnetic disc apparatus, the hub 2 is set on the disc table 20 under the suction by the magnet 21. The spindle 19 is inserted through the spindle hole 3, with the driving pin 17 being intruded into the driving pin engagement hole 4. If the driving of the spindle motor is started, the driving pin 17 compresses against the spindle 19 to center the magnetic disc 1 relative to the spindle 19, with the magnetic disc 1 being run in rotation in the main cartridge body unit 7 in unison with the disc table 20.
Meanwhile, the magnetic disc 1, set on the disc table 20 for rotation in unison therewith, is rotated at an approximately mid height position between the upper and lower sides of the main cartridge body unit 7, because the disc cartridge 8 housing the magnetic disc 1 is loaded on the cartridge loading unit in position in the height-wise direction. That is, the magnetic disc 1 is run in rotation in a manner free of contact with the upper or lower inner surfaces of the main cartridge body unit 7.
The magnetic disc apparatus is provided with a magnetic head apparatus 25 for recording and/or reproducing information signals on or from the magnetic disc 1 run in rotation by the disc rotation unit. Referring to FIG. 1, the magnetic disc apparatus 25 includes a main carriage member 26, mounted on a base, not shown, for movement radially of the magnetic disc 1 set on the disc table 20, and adapted for being fed radially of the magnetic disc by a feed mechanism, not shown. On the lower end of the main carriage member 26 is protuberantly formed a first head supporting arm 27 extended towards the lower surface of the magnetic disc 1 set on the disc table 20. On the upper end face of the main carriage member 26, the proximal end of a second head supporting arm 28, extending for facing the first head supporting arm 27 on the upper surface of the magnetic disc 1 set on the disc table 20, is mounted via a spring plate 29 for rotation towards and away from the magnetic disc 1.
Meanwhile, the second head supporting arm 28 is rotationally biased so that its distal end approaches to the magnetic disc 1 on the disc table 20 under the bias of the spring plate 29.
On opposing surfaces of the distal ends of the first and second head supporting arms 27, 28, extended on the upper and lower surfaces of the magnetic disc 1, are mounted first and second magnetic heads 29, 30. These first and second magnetic heads 29, 30 are each of a height Hl such that the magnetic heads 29, 30 are intruded via the recording and/or reproducing apertures 10, 11 into the main cartridge body unit 7 of the disc substrate 8 loaded in position in the height-wise direction on the cartridge loading unit into contact with both major surfaces of the magnetic disc being run in rotation in the main cartridge body unit 7, as shown in FIG. 1. That is, the first and second magnetic heads 29, 30 are each of a height Hl such that the magnetic heads 29, 30 are intruded into the main cartridge body unit 7 into contact with both major surfaces of the magnetic disc being run in rotation at an intermediate position between the upper and lower surfaces of the main cartridge body unit 7, without permitting the first and second head supporting arms 27, 28 extended on the upper and lower sides of the main cartridge body unit 7 to be contacted with the main cartridge body unit 7.
Meanwhile, the second head supporting arm 28, extended on the upper side of the disc cartridge 8 loaded on the cartridge loading unit, is uplifted and lowered, by a head lift mechanism, not shown, between an uplifted position spaced apart from the first head supporting arm 27 as indicated by a broken line in FIG. 1, and a lowered position, close to the first head supporting arm 27, in which the second magnetic head 30 on the distal end of the arm 28 is contacted with the magnetic disc 1 loaded on the disc table 20, as indicated by a solid line in FIG. 1.
The first and second magnetic heads 29, 30 are mounted on the distal ends of the first and second head supporting arms 27, 28 via a thin-plate-shaped gimbal spring 31 flexible in two mutually perpendicular directions, as shown in FIG. 2. The gimbal spring 31 is formed by punching a spring plate. The gimbal spring 31 has the center in its surface opposite to the surface carrying the first and second magnetic heads 29, 30 supported by a pivot 32 protuberantly formed on the first and second head supporting arms 27, 28. The first and second magnetic heads 29, 30, supported by a pivot 32, is rotationally displaced in the direction indicated by arrows A and/or B in FIG. 2 so as to follow up with the elastic deformation of the gimbal spring 31 about the pivot 32 as center.
When recording and/or reproducing information signals on or from the magnetic disc 1, the first and second magnetic heads 29, 30 are kept in sliding contact with the both major surfaces of the magnetic disc 1, run in rotation in unison with the disc table 20, as shown in FIG. 1. During rotation of the magnetic disc 1, surface deviation of the disc from the plane of rotation, in which the magnetic disc is deviated in the up-and-down direction, without being rotated in the in-plane direction, tends to be produced. In case of occurrence of the deviation of the disc from the plane of rotation, the first and second magnetic heads 29, 30 are rotationally displaced in the direction indicated by arrows A and/or B in FIG. 2, so as to follow up with the displacement of the magnetic disc 1, in order to keep the state of stable sliding contact with the magnetic disc 1. Thus, the first and second magnetic heads 29, 30 can correctly access the recording track formed on the signal recording portion of the magnetic disc 1 to reproduce the information signals.
The first and second magnetic heads 29, 30 of the magnetic disc apparatus are of a height H1 sufficient to permit the magnetic heads to be intruded into the main cartridge body unit 7 into contact with both major surfaces of the magnetic disc run in rotation in a mid position between the upper and lower sides of the main cartridge body unit 7, and are mounted on the first and second head supporting arms 27, 28 by having the proximal ends supported by the gimbal spring 31, so that the magnetic heads can be rotationally displaced significantly about the proximal ends as supporting portions for the gimbal spring 31 as center. Thus, if external disturbances are applied to the first and second head supporting arms 27, 28, the first and second magnetic heads 29, 30 tend to be rotationally displaced significantly in the direction indicated by arrows A and/or B in FIG. 2 about the proximal ends thereof as center. If the first and second magnetic heads 29, 30 are rotationally displaced significantly in this manner, the magnetic heads are deviated from the recording track to be accessed so that it becomes impossible to realize tracking of the recording track and hence correct recording/reproduction of information signals.
There is currently proposed a magnetic disc used as a recording medium for the magnetic disc apparatus having a recording capacity of from 2 megabyte as in the conventional magnetic disc up to tens to hundreds of megabyte. In this sort of the high capacity magnetic disc, the track width is reduced, at the same time as the track pitch is reduced, for increasing the density of recording tracks formed in its signal recording portion. If, in a magnetic disc apparatus employing a magnetic disc reduced both in the track width and track pitch of the recording tracks, the magnetic heads are deviated from the recording track to be accessed by the slightest rotational displacement of the magnetic head, the magnetic head cease to be able to follow up with disc displacement caused by disturbances, such that a predetermined recording track cannot be followed to disable correct recording/reproduction of information signals.
On the other hand, the magnetic disc increased in the recording capacity is run in rotation at an rpm not less than 3000 rpm. If the magnetic head is kept in sliding contact with the magnetic disc, run in rotation at an elevated speed, both the magnetic disc and the magnetic head kept in sliding contact with each other are attrited significantly and hence are deteriorated in durability. In a magnetic disc apparatus in which the magnetic head is floated from the magnetic disc during recording/reproduction of information signals, the magnetic head supported by the gimbal spring readily undergoes rotational deviation by the slightest disturbances applied to the supporting arm supporting the magnetic head. The magnetic head having the above-mentioned larger height and supported by the head supporting arm by having the proximal end supported by the gimbal spring, the magnetic head is rotationally displaced significantly without following up with displacement of the magnetic disc. Thus, the magnetic head is offset from the recording track to be accessed to disable tracking of a pre-set recording track and hence correct recording/reproduction of information signals.